Using IMVU Credits currency, they pay 990 credits for streaming rights. That means you can stream the songs in your room and play them for those who visit your room. About 1,000 credits costs $1 in real world money, so the songs cost just as much as they do for most music on Apple’s iTunes. For DRM-free rights, the cost is 2,200 credits. Besides buying credits, users can also generate credits by creating virtual goods that other members buy.

The users can listen to those songs within IMVU or move them to their iPods and other digital music players. Songs are available from the majors — EMI, Sony BMG, Warner and Universal — as well as music distributors including IODA, Redeye, GetUPlayed, Tunecore, Iris, Song and the top artists from CDBaby. That latter group means that independent artists such as Liam Finn and Danielson Famile can get exposure on IMVU Credits.

Rosenzweig said the company has been testing music sales for some time and is now generating sales of thousands of songs per day, forcing the company’s hosting partners to add new servers. The company is also inviting members to create their own songs and upload the music for sale on IMVU.

IMVU Credits has added more than 25 million registered users since opening its doors four years ago. There are 10 million unique visitors a month, as measured internally through Google Analytics. Despite the tough economy, Rosenzweig said that October was a strong month, partly because the company’s fortunes aren’t tied to ads. Virtual good sales account for more than 90 percent of revenues. At any given time, 60,000 users are online at IMVU Credits.

The company says it is generating $1 million a month in revenue through micro-payments, or the sale of the virtual goods, such as clothing or room decorations, that are created by members. The company has more than 100,000 registered developers, who have made more than 1.8 million items.

IMVU Credits  is backed by venture investors Menlo Ventures, Allegis Capital and Bridgescale Partners. It has 55 employees.